The NRC Committee on Exposure of the American People to I-131 from the Nevada Atomic Bomb Tests included people with expertise in thyroid disease, epidemiology, risk assessment, radiobiology, dose reconstruction, health physics, public health, risk communication, clinical practice, and medical ethics. The majority of this group, which focused on the first five tasks listed above, were already serving on the NRC Committee on an Assessment of CDC Radiation Studies and had accumulated considerable experience in dose reconstruction in the course of its work for the Centers for Disease Control and Prevention (CDC). Four individuals served on both committees.

The NRC committee met five times—in December 1997, January 1998, February 1998 (two meetings), and March 1998. In an open session December 19, the NRC committee and observers received some six hours of detailed briefings on the National Cancer Institute Report by the investigators. This began with an Introduction and Overview of the Study by Dr. Bruce Wachholz, and was followed by presentations on the "Estimation of the Activities of I-131 Deposited on the Ground" by Drs. Harold Beck and Lester Machta, on the "Transfer of I-131 from Deposition on the Ground to Fresh Cows' Milk" by Mr. Paul Voillequé and Drs. Mona Dreicer and André Bouville, on "Milk Production, Utilization, Distribution and Consumption'' by Dr. Mona Dreicer, on "Dose Conversion Factors" by Dr. Jacob Robbins, on "Dose Reconstruction Methodology" by Dr. André Bouville, and finally on the "Estimated Thyroid Doses" by Drs. Lester Machta and Bruce Wachholz. These presentations were followed by a brief description of the methods employed to assess the risks of thyroid cancer resulting from the estimates of thyroid dose by Dr. Charles Land (see Appendix B). It should be noted that the estimates of the lifetime risk of thyroid cancer and the possible number of individuals so affected are not included in the two volume report but were provided to the committee in the form of a memorandum addressed to Dr. Richard Klausner, the Director of the National Cancer Institute, and subsequently a revised version as a communication to the committee. The questions raised by the committee centered on the reconstruction of the doses, and in particular, the use of kriging to estimate county values where direct measurements were not available, on the methods used to determine the uncertainties in the estimates of dose, and on the assumptions inherent in the estimates of the lifetime risk of thyroid cancer.

This briefing was followed by statements from Drs. Lynn Anspaugh, Donald Myers, Roy Shore, and F. Owen Hoffman, who performed supporting experimental research at Oak Ridge National Laboratory during the mid 1980s. Given the idiosyncratic nature of dose reconstructions, these four consultants to the committee were asked to present their views on the dosimetry and dose reconstruction used in the report, the risk factors developed by the investigators and epidemiological considerations for thyroid disease, and the appropriateness of the use of spatial interpolation and kriging to assign putative exposures where no direct measurements were available. Parenthetically, kriging is an algorithm for estimating



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